So here's another small issue with the Wii that I wasn't expecting. I finally got an SD card for the system today and promptly backed everything up out of system memory and onto the card. Then I discover - you can't save directly to the SD card from within games, nor can games read save files on the SD card. Likewise, while you can copy downloaded Virtual Console games to and from the card, you can't play them from the card. The SD card is apparently for backup and transport only - anything you want to use has to be "installed" on system memory first.
It's a bit disappointing, but system memory is comparitively huge compared to memory cards of the past, so it's not too big a problem.